1. Field of the Invention
The present invention relates to a light beam scanning device, and in particular, to a light beam scanning device which scans a photosensitive material by a plurality of light beams having respectively different wavelengths which are selected in accordance with the spectral sensitivities of the photosensitive material.
2. Description of the Related Art
Conventionally, in the case of a color photosensitive material having a spectral sensitivities in the visible range (400 through 690 nm), a color image is recorded by scanning-exposing the color photosensitive material by light beams of the three colors of red, green and blue which have been modulated in accordance with the image signals of the respective colors. Here, generally, a laser light source such as a gas laser, a solid state laser (wavelength converted solid state laser) which uses light emitted by a semiconductor laser as excited light and which is equipped with a wavelength converting element, a semiconductor laser, or the like is used as the light source which emits the light beam. An appropriate laser light source is selected in accordance with the wavelength range. For example, the xe2x80x9cThe Journal of the Institute of Television Engineers of Japanxe2x80x9d, Vol. 36, No. 1, pp. 50-57 (1982) and Japanese Patent Application Laid-Open (JP-A) No. 60-14572 propose image recording devices which record a color image by scanning-exposing a color photosensitive material with light beams of three colors of red, green and blue which are emitted from respective gas lasers (an Hexe2x80x94Ne laser having an oscillation wavelength of 632 nm, an Ar laser having an oscillation wavelength of 514 nm, and an Hexe2x80x94Cd laser having an oscillation wavelength of 441 nm). Further, conventionally, semiconductor lasers which emit light beams of the short wavelength range have been difficult to obtain. Thus, semiconductor lasers (e.g., semiconductor lasers having an oscillation wavelength of 680 nm) have been used as laser light sources generating red light beams, and wavelength converted solid state lasers (e.g., wavelength converted solid state lasers having oscillation wavelengths of 473 nm and 532 nm) have been used as laser light sources generating green and blue light beams.
However, laser light sources other than semiconductor lasers have problems in that they are large and expensive. Further, because laser light sources other than semiconductor lasers cannot directly modulate the generated light beam, a problem arises in that the light beam must be modulated by using an external modulator such as an expensive acousto-optical modulation element (AOM) or the like. Further, in scanning optical systems using an external modulator such as an AOM or the like, the respective parts interfere with one another. Thus, a problem arises in that the angles between the optical axes of the respective light beams cannot be made small, and the device becomes large on the whole.
On the other hand, if compact and inexpensive semiconductor laser devices could be used as laser light sources which emit green and blue light beams, there would be no need for an external modulator. Thus, the entire scanning optical system could be made compact, and the manufacturing cost of the light beam scanning device could be reduced.
However, commercially available semiconductor lasers are a GaN semiconductor laser having an oscillation wavelength in a vicinity of 410 nm, an AlGaInP semiconductor laser having an oscillation wavelength of 630 to 680 nm, and an AlGa As or a GaInAsP semiconductor laser having an oscillation wavelength of 780 to 1550 nm. Only semiconductor lasers having oscillation wavelengths in these predetermined ranges can be obtained. Thus, there is the problem that scanning-exposing by light beams of desired wavelengths cannot be carried out for color photosensitive materials having spectral sensitivities in the visible range. In particular, the current situation is that, although silver halide photosensitive materials have spectral sensitivities in the 450 to 550 nm wavelength range, semiconductor lasers of oscillation wavelengths of 450 to 550 nm which emit blue and green light beams have not been put into practical use.
The present invention was developed in order to overcome the above-described drawbacks of the conventional art, and an object of the present invention is to provide a light beam scanning device which is compact and inexpensive and which can obtain light beams having light emission distributions which correspond to the spectral sensitivities of a photosensitive material.
In order to achieve the above object, a light beam scanning device of a first aspect of the present invention comprises: a plurality of light emitting elements which emit light beams of respectively different wavelengths selected in accordance with spectral sensitivities of a photosensitive material, at least one of the plurality of light emitting elements being an extremely small surface area light emitting diode whose surface area of a light emitting region is from 0.1 xcexcm2 to 64 xcexcm2; scanning means for scanning the photosensitive material by the light beams emitted from the plurality of light emitting elements.
An extremely small surface area light emitting diode is an edge emission-type light emitting diode whose light emitting region has an extremely small surface area of from 0.1 xcexcm2 to 64 xcexcm2. The light beam emitted from an extremely small surface area light emitting diode is incoherent light, and does not have strong directivity as does a laser beam. However, the light beam provides an amount of light which is required for scan-exposure. Further, the extremely small surface area light emitting diode can obtain a wide wavelength range as compared to a semiconductor laser.
As stated above, the light beam scanning device of the first aspect of the present invention is provided with an extremely small surface area light emitting diode as a light emitting element. Thus, a light beam having a light emission distribution which corresponds to the spectral sensitivity of a photosensitive material can be obtained, and the photosensitive material can be scanned by this light beam. Further, in the same way as a semiconductor laser, the extremely small surface area light emitting diode is compact and low cost, and the light beam can be directly modulated such that no expensive external modulator is required. Thus, the light beam scanning device can be made compact, and the manufacturing cost of the light beam scanning device can be reduced.
In a light beam scanning device of a second aspect of the present invention, in the first aspect, the plurality of light emitting elements are light emitting elements which can be directly modulated.
In a light beam scanning device of a third aspect of the present invention, in the first aspect, the photosensitive material is a color photosensitive material having spectral sensitivities in a visible range, and the plurality of light emitting elements are a light emitting element which emits a light beam in a blue wavelength range, a light emitting element which emits a light beam in a green wavelength range, and a light emitting element which emits a light beam in a red wavelength range.
The light beam scanning device of the third aspect of the present invention is provided with three light emitting elements which are selected in accordance with the spectral sensitivities of a color photosensitive material which has spectral sensitivities in the visible range, and which emit a light beam of the blue wavelength range, a light beam of the green wavelength range, and a light beam of the red wavelength range. An extremely small surface area light emitting diode, whose surface area of the light emitting region is from 0.1 m2 to 64 xcexcm2 used for any of these light emitting elements. The scanning means scans the photosensitive material with the three color light beams emitted from the three light emitting elements including the extremely small surface area light emitting diode.
In a case in which the photosensitive material is a color photosensitive material having spectral sensitivities in the visible range, three light emitting elements are used which are selected in accordance with the spectral sensitivities and which emit a light beam in the blue wavelength range, a light beam in the green wavelength range, and a light beam in the red wavelength range. By using an extremely small surface area light emitting diode whose surface area of the light emitting region is from 0.1 xcexcm2 to 64 xcexcm2 as any of the light emitting elements, a light beam having a light emission distribution corresponding to the spectral sensitivity of the color photosensitive material can be obtained.
The light emitting element which emits a light beam in the blue wavelength range, the light emitting element which emits a light beam in the green wavelength range, and the light emitting element which emits a light beam in the red wavelength range can be structured by a combination of various light emitting elements. For example, as in the light beam scanning device of the fourth aspect of the present invention, the light emitting element which emits a light beam in a blue wavelength range and the light emitting element which emits a light beam in a green wavelength range are light emitting elements which are formed by GaN semiconductor materials.
In the light beam scanning devices of the fifth and sixth aspects of the present invention, in the third aspect, the light emitting element which emits a light beam in a blue wavelength range is an extremely small surface area light emitting diode, the light emitting element which emits a light beam in a green wavelength range is a wavelength converted solid state laser, and the light emitting element which emits a light beam in a red wavelength range is a semiconductor laser; and the light emitting element which emits a light beam in a blue wavelength range is an extremely small surface area light emitting diode, the light emitting element which emits a light beam in a green wavelength range is a second harmonic generation laser, and the light emitting element which emits a light beam in a red wavelength range is a semiconductor laser. Here, a laser, which uses light emitted by a semiconductor laser as excited light and which has a wavelength converting element for converting the excited light into a second harmonic, may be used as the second harmonic generation laser. A waveguide type wavelength converting element having a periodic domain reversing structure is suitably used as the wavelength converting element which converts the excited light into a second harmonic.
In the light beam scanning device of the seventh aspect of the present invention, in the third aspect, the light emitting element which emits a light beam in a blue wavelength range is a GaN semiconductor laser, the light emitting element which emits a light beam in a green wavelength range is an extremely small surface area light emitting diode, and the light emitting element which emits a light beam in a red wavelength range is a semiconductor laser.
In the light beam scanning device of the eighth aspect of the present invention, in the third aspect, the light emitting element which emits a light beam in a blue wavelength range and the light emitting element which emits a light beam in a green wavelength range are extremely small surface area light emitting diodes, and the light emitting element which emits a light beam in a red wavelength range is a semiconductor laser.
In the light beam scanning device of the ninth aspect of the present invention, in the fourth aspect, the light emitting element which emits a light beam in a blue wavelength range and the light emitting element which emits a light beam in a green wavelength range are edge emission-type light emitting diodes, and the light emitting element which emits a light beam in a red wavelength range is a semiconductor laser.
In the light beam scanning device of the tenth aspect of the present invention, in the first aspect, the photosensitive material is a silver halide photosensitive material. A silver halide photosensitive material has spectral sensitivities in the wavelength range of 450 to 550 nm. However, the current situation is that a semiconductor laser emitting a light beam of an oscillation wavelength of 450 nm to 550 nm has not been put into practical use. However, an extremely small surface area light emitting diode which emits a light beam in this wavelength range can be obtained. Thus, by using an extremely small surface area light emitting diode for the light emitting element which emits a light beam in this wavelength range, a light beam which corresponds more to the spectral sensitivity of a silver halide photosensitive material can be scanned.